1. Technical Field
The present invention relates to a spindle motor.
2. Description of the Related Art
Generally, in a spindle motor used as a driving device of a recording disk such as a hard disk, or the like, lubricating fluid such as oil, or the like, stored in a gap between a shaft and a sleeve during rotation of the motor and a hydrodynamic bearing using dynamic pressure generated by the lubricating fluid have been variously used. In addition, the hydrodynamic bearing is generally configured of a radial bearing part and a thrust bearing part. The radial bearing part has a herringbone groove formed therein to thereby generate dynamic pressure in a journal section, and the thrust bearing part has a herringbone groove or a spiral groove to thereby generate the dynamic pressure in a thrust surface.
However, in the case of the spindle motor according to the prior art, the thrust bearing part is formed in a micro-gap between a lower portion of a hub and an upper portion of the sleeve to lead to large frictional force, thereby causing large power consumption.
Hereinafter, problems of the spindle motor according to the prior art will be described in more detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view schematically showing the spindle motor according to the prior art; and FIG. 2 is a cross-sectional view schematically showing a thrust bearing part of the spindle motor according to the prior art. As shown in FIGS. 1 and 2, the spindle motor 100 is configured to include a rotating part including a rotating shaft 110, a hub 120, and a magnet 130, and a fixing part including a sleeve 140, a bracket 150, a stator 160, and a support 170.
The rotating shaft 110 is rotatably supported by the sleeve 140 and has the hub 120 coupled thereto, and the hub 120 has the magnet 130 fixed to an inner circumferential surface thereof.
In addition, the sleeve 140 has the bracket 150 coupled to an outer circumferential surface thereof by press-fitting, adhesion, or the like, the bracket 150 has the stator 160 coupled to an outer circumferential portion thereof by press-fitting, adhesion, or the like, and the support 170 is coupled to the sleeve 140 while supporting the rotating shaft 110.
In the spindle motor 100 configured as described above, a micro-gap is formed between an upper end of the sleeve 140 and a lower end of the hub 120 and is filled with oil as lubricating fluid, such that a thrust hydrodynamic bearing part 180 is formed, and a dynamic pressure generating groove 181 is formed shown in FIG. 2. The dynamic pressure generating groove 181 is formed as a herringbone groove 181 or a spiral groove.
In addition, a micro-gap is formed between an outer circumferential portion of the rotating shaft 110 and an inner circumferential portion of the sleeve 140 and is filled with oil as lubricating fluid, such that a radial hydrodynamic bearing part 190 is formed. The radial hydrodynamic bearing part 190 has a dynamic pressure generating groove formed in a radial direction of the rotating shaft.
Therefore, dynamic pressure unbalance is generated in the thrust hydrodynamic bearing part 180 due to tilting, or the like, of the hub during the assembling of the hub 120 and the sleeve 140. In addition, when pattern unbalance is generated by the herringbone groove 181 or the spiral groove formed in the thrust hydrodynamic bearing part 180, dynamic pressure unbalance is generated. Furthermore, efficiency in power consumption is reduced due to frictional force of the thrust hydrodynamic bearing part 180 implemented to have a wide area.